Corrected entry: When the boys dig up Kyle's dead grandmother, the last name on the tombstone is "Broflovski." But when the cemetery people go to Kyle's house to tell his parents what happened, they tell his mother "your mother" has been dug up. Unless her maiden name is also "Broflovski," which is unlikely, the dead woman would have to be Kyle's father's mother.
Corrected entry: During the dreidel song Kyle's mother comes in, but you can barely hear her voice. This is because the woman that played all of the female voices committed suicide in the middle of the 3rd season, so they had to find another person and they turned down the sound of her voice so no one would hear any differences between the real voice and the voice they used in this episode.